Hitherto, polyurethane resins have been used in a wide variety of forms including foams, adhesives, fibers, soft or rigid elastomers, ink binders, synthetic leathers and paints.
They are mainly prepared by the reaction of an organic diisocyanate compound with polyol compounds.
The polyol compounds which have been employed include polyether polyols such as polypropylene glycols, polytetramethylene glycols, polyester polyols which are derived from a divalent carboxylic acid such as adipic acid, and a polyhydric alcohol or a polylactone-polyol which is obtained by the reaction of a lactone monomer with an alcohol.
A variety of polyol compounds have been used to produce polyurethane resin which is used for many kinds of purposes.
However, as polyether polyols have ether bonds, the urethane resin which is produced employing them has the disadvantage of being poor in heat resistance and in outdoor durability.
The urethane resin which is produced by employing polyester or polylactone-polyols has the disadvantage of being poor in water resistance, thought to be due to presence of ester bonds.
The use of polyols having carbonate bonds in the molecular structure has been proposed to produce novel urethane resins which overcome the foregoing disadvantages.
The polycarbonate-polyols which are used more widely than any other type of polyol compound is the polyol having a carbonate bond in the molecular structure containing 1,6-hexanediol in the main chain of the molecular structure, as shown by formula (I): ##STR1##
The polycarbonate-diol having 1,6-hexanediol structures in the main chain can produce a polyurethane resin having a very good balance of various properties, including mechanical strength, excellent resistance under high heat and moisture conditions, etc., thereby maintaining a good balance of properties, and has also the advantage of being easy to produce on an industrial basis.
Furthermore, it is known that a urethane resin having an improved mechanical strength can be prepared from a diol mixture composed of 1,6-hexanediol containing cyclohexane dimethnol.
Still further, German Patent No.1921866 and 1770618 teach that a polycarbonate-polyol composition with which a urethane polymer having high density and high tenacity is prepared by a reaction with a diisocyanate compound, can be prepared by an ester interchange reaction of a mixture composed of a diol and a triol with an aliphatic or aromatic carbonate compound.
In addition, Japanese Examined Application Publication (Kokoku) No. 39650/1982 [entitled: A process for preparing a polycarbonate-triol]teaches a process for preparing a polycarbonate-triol being liquid at room temperatures.
The process comprises an ester interchange reaction of an aromatic carbonate compound with a primary aliphatic triol (for example, trimethylolpropane or trimethylolethane) and an aliphatic or alicyclic diol.
However, the polycarbonate-polyol composition prepared by the ester interchange reaction of the aromatic carbonate compound with the mixture composed of the diol and triol contains not only a free aromatic alcohol, but also by-produced phenyl terminated-polycarbonate compounds.
It has been pointed out that a polyurethane resin prepared by the reaction of the polycarbonate-polyol composition with a diisocyanate compound does not exhibit sufficient properties because of the by-products.
In the case that a polycarbonate-polyol composition is prepared by the ester interchange reaction of an aliphatic carbonate compound with the mixture composed of the diol and triol, an aliphatic alkyl-terminated polycarbonate compound is by-produced.
The polyurethane prepared by the polycarbonate-polyol composition containing the aliphatic alkyl-terminated polycarbonate compound does not exhibit sufficient properties.
The Japanese Patent Application Publication(Kokoku) No.1978/42359 [corresponding to US 4,013,702--entitled:Process for the purification of Polycarbonates] teaches that a polycarbonate-polyol composition can be refined by adding water thereto.
Presently it is desireable that coating compositions be of the low pollution type, or be of a valuable components saving type and or of an energy saving type.
A specific example of successful coating compositions having these advantages is a ultraviolet-radiation curable type.
This type coating composition contains a ultra violet-radiation curable compound having at least two acryl or methcryl groups, a polymerizable monomer and various additives.
This type coating composition contains practically no volatile components such as solvents and, only partially contains polymerizable monomers which function as a reactive diluent to form protective coating layer together with ultraviolet-radiation curable main components.
Still further, an electron-beam curable coating composition can be cured as well as the ultraviolet-radiation curable composition without a photo-initiator, or a photo-sensitizer.
Such ultraviolet-radiation curable or electron-beam curable coating compositions have been used in the fields of coatings, adhesives, vehicles for a printing ink, a solder resist ink, materials for anastatic printings, linings for a mortar floor, coatings for PVC tiles and outer coatings for optical glass fibers or plastic molds.
Fundamental properties of the cured articles(specifically, coating layers, inks, films) depend remarkably upon the type of photo (ultraviolet-radiation or electron-beam) curable prepolymer which is the base-resin.